Polarizing plate and optical display including the same

ABSTRACT

A polarizing plate includes a polarizer, and a protective film on one side of the polarizer and including a reverse dispersion liquid crystal coating layer having λ/4 retardation. An optical display panel includes the polarizing plate. The polarizing plate has a depolarization function and allows for viewing of the display panel through polarizing sunglasses.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2013-0011025, filed in the Korean IntellectualProperty Office on Jan. 31, 2013, the entire content of which isincorporated herein by reference.

BACKGROUND

1. Field

The following description relates to a polarizing plate and an opticaldisplay including the same.

2. Description of the Related Art

Polarizing sunglasses include a polarizing film which filters light fromthe outside by allowing only light incident at a certain angle to bevisible. Generally, polarizing sunglasses are used during driving orfishing.

However, when a display panel including a polarizing plate is viewedthrough polarizing sunglasses, the screen of the display may not bevisible due to the perpendicular alignment of the polarizing plate ofthe display panel and the polarizing film of the sunglasses.

FIG. 1(A) shows a display including a liquid crystal panel 10, an upperpolarizer 20 formed on an upper side of the liquid crystal panel 10, anda lower polarizer 30 formed on a lower side of the liquid crystal panel10. If a polarizing film 40 of the polarizing sunglasses has anabsorption axis parallel to that of the upper polarizer 20, a displayimage can be visible (indicated by the “O” mark on the left side).However, if the polarizing film 40 of the polarizing sunglasses has anabsorption axis perpendicular to that of the upper polarizer 20, thedisplay image is not visible (indicated by the “X” mark on the rightside).

In an attempt to improve visibility, a polarizing plate as shown in FIG.6 is usually used as an upper polarizing plate of the display. As shownin FIG. 6, a polarizing plate 4000 includes upper and lower protectivefilms 340 and 320 formed on upper and lower sides of a polarizer 330,respectively; a retardation film 360 stacked on an upper side of theupper protective film 340 via an adhesive 350; and a hardcoated-triacetyl cellulose film 380 stacked on an upper side of theretardation film 360 via an adhesive 370 to address low surface hardnessof the retardation film 360. The polarizing plate 4000 is bonded to adisplay panel 300 via an adhesive 310.

The retardation film usually includes polycarbonate, polyethyleneterephthalate, cycloolefin films, or the like. However, the polarizingplate prepared in this manner is thick and has low yield.

SUMMARY

In accordance with one or more aspects of embodiments of the presentinvention, a polarizing plate includes: a polarizer; and a protectivefilm on an upper side of the polarizer and including a reversedispersion liquid crystal coating layer.

In accordance with another aspect of the present invention, an opticaldisplay includes the polarizing plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(A) and 1(B) are conceptual diagrams illustrating depolarizationby a polarizing plate.

FIG. 2 is a cross-sectional view of a polarizing plate according to oneembodiment of the present invention.

FIG. 3 is a cross-sectional view of a polarizing plate according toanother embodiment of the present invention.

FIG. 4 is a cross-sectional view of an optical display according to oneembodiment of the present invention.

FIG. 5 shows the results of the operating states of the LCD panels towhich polarizing plates according to Examples and Comparative Exampleswere bonded. Here, A shows the results of Examples 1 and 2 andComparative Example 2, and B shows the results of Comparative Example 1.

FIG. 6 is a cross-sectional view of a prior art polarizing plate fordepolarization.

DETAILED DESCRIPTION

Embodiments of the present invention will be described with reference tothe accompanying drawings. It should be understood that the presentinvention may be embodied in different ways and is not limited to thefollowing embodiments. In the drawings, portions irrelevant to thedescription have been omitted for clarity. Like components are denotedby like reference numerals throughout the drawings and specification.

As used herein, terms such as “upper side” and “lower side” are definedwith reference to the accompanying drawings. Thus, it will be understoodthat the term “upper side” can be used interchangeably with the term“lower side”.

Expressions such as “at least one of” and “one of,” when preceding alist of elements, modify the entire list of elements and do not modifythe individual elements of the list. Further, the use of “may” whendescribing embodiments of the present invention refers to “one or moreembodiments of the present invention.”

In accordance with one embodiment of the present invention, a polarizingplate may include a polarizer, and a protective film on an upper side ofthe polarizer and including a reverse dispersion liquid crystal coatinglayer. The reverse dispersion liquid crystal coating layer has circularpolarization due to λ/4 in-plane retardation and thus can providedepolarization when a display panel including the polarizing plate as anupper polarizing plate of the display panel is viewed through polarizingsunglasses.

FIG. 1 is a conceptual diagram illustrating depolarization by apolarizing plate when a display panel is viewed through polarizingsunglasses. FIG. 1(A) shows a polarizing plate free from a reversedispersion liquid crystal coating layer 50, and FIG. 1(B) shows apolarizing plate including the reverse dispersion liquid crystal coatinglayer 50.

Referring to FIG. 1(A), when a display including a liquid crystal panel10, an upper polarizer 20 on an upper side of the liquid crystal panel10, and a lower polarizer 30 on a lower side of the liquid crystal panel10 is viewed through polarizing sunglasses 40, images on the display maynot be visible (a case denoted by “X” on the right side) if the upperpolarizer 20 has an absorption axis perpendicular to that of thepolarizing sunglasses 40. In contrast, referring to FIG. 1(B), since thereverse dispersion liquid crystal coating layer 50 achieves circularpolarization due to λ/4 retardation and thus depolarizes the upperpolarizer 20, the images on the display can be visible when viewedthrough the polarizing sunglasses 40 (a case denoted by “O” on the rightside), even when the polarizing sunglasses 40 have an absorption axisperpendicular to that of the upper polarizer 20.

The polarizing plate may further include a functional layer on onesurface of the protective film, for example, on an upper side of theprotective film. The functional layer may be a hard coating layer, orthe like. The hard coating layer improves hardness of the protectivefilm and thus can improve hardness of the polarizing plate. In oneembodiment, the functional layer may have a thickness of about 3 μm toabout 50 μm.

The polarizing plate may further include a λ/2 retardation layer betweenthe protective film and the reverse dispersion liquid crystal coatinglayer. The inclusion of the λ/2 retardation layer helps the polarizingplate to realize circular polarization.

The polarizing plate may further include a protective film on a lowerside of the polarizer. Since the polarizing plate further includes theprotective film, direct contact of the polarizer with the panel can beprevented, thereby reducing or preventing changes in polarizationperformance of the polarizer.

Hereinafter, a polarizing plate according to one embodiment of theinvention will be described with reference to FIGS. 2 and 3.

FIG. 2 is a sectional view of a polarizing plate according to oneembodiment of the present invention. Referring to FIG. 2, a polarizingplate 1000 may include: a polarizer 100; a reverse dispersion liquidcrystal coating layer 105 on an upper side of the polarizer 100; a firstprotective film 110 on an upper side of the reverse dispersion liquidcrystal coating layer 105; a hard coating layer 115 on an upper side ofthe first protective film 110; and a second protective film 120 on alower side of the polarizer 100.

The reverse dispersion liquid crystal coating layer 105 may have anin-plane retardation (Re) of about 100 nm to about 170 nm at awavelength of 550 nm, as calculated using Equation 1, and anout-of-plane retardation (Rth) of about 60 nm to about 120 nm at awavelength of 550 nm, as calculated using Equation 2. For example, thereverse dispersion liquid crystal coating layer 105 may have an in-planeretardation at a wavelength of 550 nm of about 100, 105, 110, 115, 120,125, 130, 135, 140, 145, 150, 155, 160, 165 or 170 nm, and anout-of-plane retardation at a wavelength of 550 nm of about 60, 65, 70,75, 80, 85, 90, 95, 100, 105, 110, 115 or 120 nm. Within any of theseranges, the polarizing plate can exhibit a high degree ofdepolarization.

Re=(nx−ny)×d   Equation 1

Rth=((nx+ny)/2−nz)×d   Equation 2

In Equations 1 and 2, nx, ny and nz are the refractive indices in x-, y-and z-axis directions, respectively, and d is the thickness of theliquid crystal coating layer in nm.

The reverse dispersion liquid crystal coating layer 105 may have anx-axis direction corresponding to the direction of coating of thereverse dispersion liquid crystal coating layer, a y-axis directioncorresponding to the direction perpendicular to the direction of coatingof the reverse dispersion liquid crystal coating layer, and a z-axisdirection corresponding to the thickness direction of the reversedispersion liquid crystal coating layer. The x-, y- and z-axes may beperpendicular to each other.

The reverse dispersion liquid crystal coating layer 105 may have athickness of about 0.5 μm to about 10 μm. Within this range, thepolarizing plate can exhibit circular polarization.

The reverse dispersion liquid crystal coating layer 105 may include atleast one of nematic liquid crystals, cholesteric liquid crystals, andchiral smectic C liquid crystals. In one embodiment, the reversedispersion liquid crystal coating layer 105 includes nematicmonomolecular liquid crystals.

The reverse dispersion liquid crystal coating layer 105 may be preparedby any suitable method. For example, the reverse dispersion liquidcrystal coating layer 105 may be prepared by coating an alignment layeronto one surface of a protective film; drying and curing the alignmentlayer; rubbing the alignment layer; and coating a liquid crystal coatingsolution including a liquid crystal polymer, a curing agent, a levelingagent and a solvent onto the alignment layer, followed by curing.

In some embodiments, coating the alignment layer includes coating analignment layer resin onto the protective film in the form of asolution. The alignment layer resin may include any suitable resin, forexample, monomers, oligomers or the like, which have a polymericunsaturated bond, such as monofunctional (meth)acrylates orpolyfunctional (meth)acrylates, ethers, amino groups, or the like.

In some embodiments, rubbing the alignment layer includes aligning thecured alignment layer in a certain direction on a surface by forcing thecured alignment layer to pass through a rubbing device. Rubbing thealignment layer may be performed, for example, by preparing a rubbingroll, to which a velvet-like cloth implanted with fibers such as rayon,nylon, cotton, aramid or the like is attached, and treating thealignment layer with the roll rotating at high speed, but embodiments ofthe invention are not limited thereto.

The liquid crystal layer may be prepared by coating the liquid crystals,followed by curing.

In some embodiments, liquid crystals are coated onto the surface of thealignment resin after the latter has been subjected to coating anddrying. Coating may be performed by spin coating, without being limitedthereto.

The polarizer 100 may include any suitable polarizer having polarizationcapabilities. In one embodiment, the polarizer may be a linearpolarizer, which is formed by adsorption and alignment of a dichroicmaterial to a polyvinyl alcohol resin, and is capable of absorbinglinearly polarized light having an oscillation plane of a firstdirection and transmitting linearly polarized light having anoscillation plane of a second direction orthogonal to the firstdirection. The dichroic material may include iodine or dichroic organicdyes. In some embodiments, the polarizer may be prepared by uniaxiallystretching a polyvinyl alcohol resin film, followed by dyeing the filmwith a dichroic material followed by treatment with boric acid.

The polarizer 100 may have a thickness of about 4 μm to about 30 μm.

The first protective film 110 may be a transparent protective layer andmay protect the polarizer. Specifically, the first protective film 110may be formed of at least one of cellulose, polyester, cyclicpolyolefin, polycarbonate, polyether sulfone, polysulfone, polyamide,polyimide, polyolefin, polyarylate, polyvinyl alcohol, polyvinylchloride, or polyvinylidene chloride films. In some embodiments, theprotective film 110 is a triacetyl cellulose (TAC) film which is acellulose film.

The first protective film 110 may have a thickness of about 10 μm toabout 1000 μm, and in some embodiments of about 10 μm to about 100 μm orabout 20 μm to about 80 μm. Within this range, the first protective film110 can be stacked on the polarizer.

The hard coating layer 115 may be prepared by coating a composition forhard coating onto one surface of the first protective film, followed bydrying, but embodiments of the invention are not limited thereto. Thecomposition for hard coating may include, but is not limited to anacrylic resin or a urethane acrylic resin.

The second protective film 120 may be a transparent protective layer,for example, a film formed of at least one of cellulose, polyester,cyclic polyolefin, polycarbonate, polyether sulfone, polysulfone,polyamide, polyimide, polyolefin, polyarylate, polyvinyl alcohol,polyvinyl chloride, or polyvinylidene chloride films.

The second protective film 120 may have a thickness of about 10 μm toabout 1000 μm, and in some embodiments of about 10 μm to about 100 μm orabout 20 μm to about 80 μm. Within this range, the second protectivefilm 120 can be stacked on the polarizer.

The polarizer, the reverse dispersion liquid crystal coating layer, thefirst protective film and the second protective film may be bonded toeach other by a bonding layer, although the bonding layer is not shownin FIG. 2. The bonding layer may be formed of a water-based bondingagent, a pressure-sensitive bonding agent or the like, such as apolyvinyl alcohol bonding agent, a (meth)acrylic bonding agent, or thelike.

The polarizing plate may have a thickness of about 100 μm to about 200μm, and in some embodiments of about 100 μm to about 160 μm. Within anyof these ranges, the polarizing plate can be applied to a liquid crystaldisplay.

The polarizing plate may be used as an upper polarizing plate 205 of adisplay panel. As shown in FIG. 4, the upper polarizing plate 205 of thedisplay panel may refer to a polarizing plate formed on a side of adisplay panel 200 opposite to the side facing the backlight unit 220.

The polarizing plate may be stacked on the display panel via an adhesivelayer, although the adhesive layer is not shown in FIG. 2. In someembodiments, the adhesive layer may include a (meth)acrylic copolymer asan adhesive resin, but is not limited thereto.

FIG. 3 is a sectional view of a polarizing plate according to anotherembodiment of the present invention. Referring to FIG. 3, a polarizingplate 2000 may include: a polarizer 100; a reverse dispersion liquidcrystal coating layer 105 on an upper side of the polarizer 100; a λ/2retardation layer 125 on an upper side of the reverse dispersion liquidcrystal coating layer 105; a first protective film 110 on an upper sideof the λ/2 retardation layer 125; a hard coating layer 115 on an upperside of the first protective film 110; and a second protective film 120on a lower side of the polarizer 100. The polarizing plate 2000 issubstantially the same as the polarizing plate described above, exceptthat the λ/2 retardation layer 125 is included between the reversedispersion liquid crystal coating layer 105 and the first protectivefilm 110.

The λ/2 retardation layer 125 may have an in-plane retardation (Re) ofabout 240 nm to about 300 nm at a wavelength of 550 nm, as calculatedusing Equation 3, and an out-of-plane retardation (Rth) of about 120 nmto about 270 nm at a wavelength of 550 nm, as calculated using Equation4. For example, the λ/2 retardation layer 125 may have an in-planeretardation at a wavelength of 550 nm of about 240, 245, 250, 255, 260,265, 270, 275, 280, 285, 290, 295 or 300 nm, and an out-of-planeretardation at a wavelength of 550 nm of, about 120, 125, 130, 135, 140,145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 210,215, 220, 225, 230, 235, 240, 245, 250, 255, 260, 265 or 270 nm. Withinany of these ranges, the polarizing plate can exhibit circularpolarization.

Re=(nx−ny)×d   Equation 3

Rth=((nx+ny)/2−nz)×d   Equation 4

In Equations 3 and 4, nx, ny and nz are the refractive indices in thex-, y- and z-axis directions, respectively, and d is the thickness ofthe λ/2 retardation layer in nm.

The λ/2 retardation layer may have an x-axis direction corresponding tothe direction of coating of the λ/2 retardation layer, a y-axisdirection corresponding to the direction perpendicular to the directionof coating of the λ/2 retardation layer, and a z-axis directioncorresponding to the thickness direction of the λ/2 retardation layerThe x-, y- and z-axes may be perpendicular to each other. In otherwords, the x-axis of the λ/2 retardation layer corresponds to thelongitudinal direction of the film (MD, machine direction), the y-axiscorresponds to the width direction of the film (TD, transversedirection), and the z-axis direction corresponds to the thicknessdirection of the film, and the x-, y- and z-axes may be perpendicular toeach other.

The λ/2 retardation layer may have a thickness of about 0.5 μm to about70 μm. Within this range, the polarizing plate can exhibit circularpolarization.

The λ/2 retardation layer may have any suitable form without limitationso long as the layer provides λ/2 retardation. For example, the λ/2retardation layer may be a liquid crystal coating layer or a film. Inone embodiment, the λ/2 retardation layer may be a liquid crystalcoating layer formed by the same method as the aforementioned liquidcrystal coating layer. In another embodiment, the λ/2 retardation layermay be a film. For example, the λ/2 retardation layer may be a filmformed of olefins such as a cycloolefin polymer (COP), acrylics,celluloses, or a mixture thereof.

The λ/2 retardation layer 125 may be stacked on the reverse dispersionliquid crystal coating layer 105 via an adhesive layer, although theadhesive layer is not shown in FIG. 3. The adhesive layer may include anadhesive, such as a (meth)acrylic copolymer, as an adhesive resin. Theadhesive layer may have a thickness of about 1 μm to about 30 μm.

In accordance with another aspect of the present invention, an opticaldisplay may include the polarizing plate according to embodiments of thepresent invention. FIG. 4 is a sectional view of an optical displayaccording to one embodiment of the present invention.

Referring to FIG. 4, according to one embodiment of the invention, anoptical display 3000 may include: a display panel 200; a firstpolarizing plate 205 on an upper side of the display panel 200; and asecond polarizing plate 210 on a lower side of the display panel 200 andbetween the display panel 200 and a backlight unit 220., The firstpolarizing plate 205 may be the polarizing plate according to anembodiment of the invention.

The second polarizing plate 210 may be a conventional polarizing plateincluding a polarizer. In one embodiment, the second polarizing plate210 may include: a polarizer; a first optical film on an upper side ofthe polarizer; and a second optical film on a lower side of thepolarizer. The optical film may be at least one of a protective film ora retardation film.

The display panel 200 may include a liquid crystal layer, which includesliquid crystals of a horizontal mode, such as in-plane switching (IPS)mode, fringe field switching (FFS) mode or the like, a verticalalignment mode, or a twisted nematic (TN) mode.

A method of using the polarizing plate according to embodiments of theinvention may include viewing a display screen of the optical displaythrough polarizing sunglasses.

Hereinafter, the present invention will be described with reference tosome examples. However, it should be noted that these examples areprovided for illustration only and are not to be construed in any way aslimiting the present invention.

EXAMPLE 1

A polarizer was prepared by dyeing of a material for polarizers,followed by stretching, and the like. Specifically, a polyvinyl alcoholfilm (PS60, Kuraray Co., Ltd., Japan, thickness: 60 μm) was stretched to2 times its initial length at 50° C., followed by iodine adsorption ontothe polyvinyl alcohol film, and stretching again to 2.5 times the lengthof the stretched film in a boric acid solution at 40° C., therebypreparing a polarizer (thickness: 22 μm).

A reverse dispersion liquid crystal coating layer (liquid crystals:nematic monomolecular liquid crystals, thickness: 3.5 μm, Re: 148 nm andRth: 100 nm at a wavelength of 550 nm) was coated onto one surface of aprotective film HC TAC (hard coating-triacetyl cellulose, DNP Co., Ltd.,Japan, thickness: 30 μm) by die coating.

The HC TAC including the reverse dispersion liquid crystal coating layerformed thereon was stacked on an upper side of the polarizer such thatthe reverse dispersion liquid crystal coating layer was bonded to thepolarizer. A TAC film (TAC, DNP Co., Ltd, thickness: 40 μm) was bondedto a lower side of the polarizer as a protective film, thereby preparinga polarizing plate having the structure shown in FIG.

2.

EXAMPLE 2

A polarizing plate having the structure shown in FIG. 3 was prepared inthe same manner as in Example 1 except that a λ/2 retardation layer(thickness: 43 μm, Re: 260 nm and Rth: 130 nm at a wavelength of 550 nm)was further formed between the HC TAC film (used as the protective film)and the reverse dispersion liquid crystal coating layer.

COMPARATIVE EXAMPLE 1

A polarizing plate was prepared as in Example 1 except that the reversedispersion liquid crystal coating layer was omitted.

COMPARATIVE EXAMPLE 2

A polarizing plate having the structure shown FIG. 6 was prepared as inExample 1 except that a TAC film (as a protective film) and acycloolefin film (ZD12-141158, Zeon Co., Ltd., thickness: 33 μm) (as aretardation film) were stacked instead of the reverse dispersion liquidcrystal coating layer.

The polarizing plates prepared in Examples 1 and 2 and ComparativeExamples 1 and 2 were evaluated as to the following properties. Resultsare shown in Table 1 and FIG. 5.

(1) Optical properties: transmittance, reflectance and degree ofpolarization of the polarizing plate were measured using a V-7100 (JASCOCo., Ltd., Japan).

(2) Haze: haze was measured on the polarizing plate using a haze meter.

(3) Visibility of screen during operation of display: after thepolarizing plate was assembled as an upper polarizing plate of an LCDdisplay panel and the LCD display panel was operated, a screen of thedisplay was viewed through polarizing sunglasses. The instances when thescreen was visible were rated as O, and the instances when the screenwas not visible were rated as X.

TABLE 1 Exam- Exam- Comparative Comparative ple 1 ple 2 Example 1Example 2 Thickness of 114 117 110 173 polarizing plate (μm)Transmittance (%) 42.5 43.2 42.5 42.10 Reflectance (%) 5.4 5.4 5.4 5.4Degree of 99.990 99.962 99.992 99.978 polarization (%) Haze (%) 1.2 1.30.8 1.4 Visibility of screen ◯ ◯ X ◯

As shown in Table 1, the polarizing plates according to embodiments ofthe present invention exhibited good optical properties and goodhardness. In addition, as shown in part A of FIG. 5, when a displayscreen with the polarizing plate according to embodiments of theinvention was viewed through the polarizing sunglasses, the screen wasvisible.

Thus, embodiments of the present invention provide a polarizing platewhich has a depolarization function and allows for viewing of a displaypanel through polarizing sunglasses. In addition, the manufacturingprocess of the polarizing plate has fewer steps, since the process oflaminating a film can be omitted.

In contrast, as shown in part B of FIG. 5, the screen of the displaypanel on which the polarizing plate of Comparative Example 1 (free fromthe liquid crystal coating layer) was mounted, could not be viewedthrough the polarizing sunglasses.

In addition, although the screen of the display panel was also visiblewhen the polarizing plate of Comparative Example 2 was used, suchpolarizing plate had a significantly larger thickness than thepolarizing plate according to embodiments of the invention.

While certain exemplary embodiments of the present invention have beenillustrated and described herein, it should be understood that variousmodifications, changes, alterations, and equivalent embodiments can bemade by those skilled in the art without departing from the spirit andscope of the invention. Instead, the scope of the present inventionshould be limited only by the accompanying claims and equivalentsthereof.

What is claimed is:
 1. A polarizing plate comprising: a polarizer; afirst protective film on a first side of the polarizer and comprising areverse dispersion liquid crystal coating layer.
 2. The polarizing plateaccording to claim 1, wherein the reverse dispersion liquid crystalcoating layer has λ/4 retardation.
 3. The polarizing plate according toclaim 1, wherein the reverse dispersion liquid crystal coating layer isformed between the polarizer and the first protective film.
 4. Thepolarizing plate according to claim 1, wherein the reverse dispersionliquid crystal coating layer has an in-plane retardation (Re) of about100 nm to about 170 nm at a wavelength of 550 nm, as calculated usingEquation 1:Re=(nx−ny)×d, wherein nx and ny are refractive indices in x- and y-axisdirections, respectively, and d is a thickness of the reverse dispersionliquid crystal coating layer in nm.
 5. The polarizing plate according toclaim 1, wherein the reverse dispersion liquid crystal coating layer hasa thickness of about 0.5 μm to about 10 μm.
 6. The polarizing plateaccording to claim 1, wherein the first protective film comprises amaterial selected from the group consisting of cellulose, polyester,cyclic polyolefin, polycarbonate, polyether sulfone, polysulfone,polyamide, polyimide, polyolefin, polyarylate, polyvinyl alcohol,polyvinyl chloride, polyvinylidene chloride films, and combinationsthereof.
 7. The polarizing plate according to claim 1, furthercomprising a hard coating layer on a side of the first protective filmopposite from the reverse dispersion liquid crystal coating layer. 8.The polarizing plate according to claim 1, further comprising a λ/2retardation layer between the first protective film and the reversedispersion liquid crystal coating layer.
 9. The polarizing plateaccording to claim 8, wherein the λ/2 retardation layer has an in-planeretardation (Re) of about 240 nm to about 300 nm at a wavelength of 550nm, as calculated using Equation 3:Re=(nx−ny)×d,   Equation 1 wherein nx and ny are refractive indices inx- and y-axis directions, respectively, and d is a thickness of the λ/2retardation layer in nm.
 10. The polarizing plate according to claim 8,wherein the λ/2 retardation layer is a liquid crystal coating layer or afilm.
 11. The polarizing plate according to claim 8, wherein the λ/2retardation layer has a thickness of about 0.5 μm to about 70 μm. 12.The polarizing plate according to claim 1, further comprising a secondprotective film on a second side of the polarizer, opposite from thefirst side.
 13. The polarizing plate according to claim 12, wherein thesecond protective film comprises a material selected from the groupconsisting of cellulose, polyester, cyclic polyolefin, polycarbonate,polyether sulfone, polysulfone, polyamide, polyimide, polyolefin,polyarylate, polyvinyl alcohol, polyvinyl chloride, polyvinylidenechloride films, and combinations thereof.
 14. An optical displaycomprising: a display panel; a first polarizing plate on a first side ofthe display panel; and a second polarizing plate between a second sideof the display panel and a backlight unit, wherein the first polarizingplate is the polarizing plate according to claim 1.